The present invention provides a microwave termination for microwave transmission line structures such as coaxial lines and the like. Prior art microwave terminations generally comprise a body serving as the ground or outer conductor and forming a cavity closed at one end, a center conductor, a dielectric bead which supports the center conductor in coaxial relationship with the body, and a resistive element within the cavity connected between the center conductor and the body. The resistive bodies of the prior art microwave terminations are found to have various configurations, for example, cylindrical and truncated cone configurations. Generally, these are symmetrically disposed about the same axis as the center conductor.
The present invention provides a novel microwave termination which has good microwave characteristics such as low voltage-standing-wave-ratio (VSWR) over a wide range of frequencies, e.g., D.C. to 18 GHz. Importantly, the termination of the present invention may be manufactured to relatively small dimensions and comprises component parts which are readily machined, or otherwise produced, and assembled.
The microwave termination of the present invention features a resistive rod or elongated cylindrical resistive element which is disposed within the cavity formed by the outer conductor and extends transversely of the axis of the center conductor, and preferably, extends perpendicularly of the axis of the center conductor, e.g., in spoke-like relationship therewith. For example, the resistive rod is electrically connected to the outer conductor or body at its opposite end portions and is electrically connected to the center conductor at a portion intermediate its ends. The intermediate portion is centrally located so as to provide a symmetrical structure. The resistive element may be a ceramic rod having a resistive layer such as a pyrolytic carbon coating of predetermined ohms per square. The microwave energy entering the termination from the coaxial line is substantially entirely dissipated in this resistive element.
Other features and advantages of the present invention will be apparent in view of the following detailed description of the preferred embodiment.